1. Field of the Invention
The present invention relates to an image processing technique that is performed on an image acquired through image capturing by an image pickup apparatus such as a digital still camera and a video camera.
2. Description of the Related Art
Various electronic image processing techniques that are performed on an image (captured image) acquired by image capturing have been conventionally proposed. For example, Japanese patent Laid-Open No. 2011-187208 discloses an image processing technique of recognizing a face of a person in a captured image to paint or blur other areas than the face, or to clip areas around the face. In addition, Japanese patent Laid-Open No. 2004-145287 discloses an image processing technique of performing determination required for a process using information on a captured image and information on an image pickup condition under which image capturing to acquire the captured image is performed. In addition, Japanese patent Laid-Open No. 2011-44825 discloses an image processing technique of acquiring information on a distance (object distance) to an object included in a captured image and performing an image restoration process thereon using image restoration filters different depending on the object distance.
Captured images acquired by image capturing through an optical system mostly include degradation due to imaging performance (such as aberration and diffraction) of the optical system. In an out-of-focus area including an object like a point light source, an uneven blur (such as a peripheral blur or a highly asymmetric blur), which while be described later, is generated due to the imaging performance. It is desirable that such an uneven blur be removed or reduced by an image process.
However, it is difficult in the image process to accurately distinguish the uneven blur generated in the out-of-focus area caused by the imaging performance of the optical system from an object having an uneven shape. Such difficulty may cause erroneous detection of an area including the uneven-shaped object as an area including the uneven blur and may cause execution of an image process on the erroneously detected area, thereby providing an image different from a desired captured image. None of Japanese patent Laid-Open Nos. 2011-187208, 2004-145287 and 2011-44825 disclose a method of detecting the uneven blur with high accuracy.